Catheter balloon

ABSTRACT

An expandable medical device or component thereof including a tubular body formed of a wrapped sheet of porous polymeric material fused together, the tubular body having a fused seam at an angle relative to the longitudinal axis of the tubular body which changes along the length of the tubular body from a first angle to a second angle greater than the first angle. The sheet of porous polymeric material is wound and then fused together such that the winding angle is less in a first longitudinal section of the tubular body compared with the winding angle in a second longitudinal section of the tubular body, in order to provide the second section with greater resistance to expansion (i.e., lower compliance) than the first section.

BACKGROUND OF THE INVENTION

This invention generally relates to medical devices, and particularly tointracorporeal devices for therapeutic or diagnostic uses such asballoon catheters, and vascular grafts.

In percutaneous transluminal coronary angioplasty (PTCA) procedures, aguiding catheter is advanced until the distal tip of the guidingcatheter is seated in the ostium of a desired coronary artery. Aguidewire, positioned within an inner lumen of a dilatation catheter, isfirst advanced out of the distal end of the guiding catheter into thepatient's coronary artery until the distal end of the guidewire crossesa lesion to be dilated. Then the dilatation catheter having aninflatable balloon on the distal portion thereof is advanced into thepatient's coronary anatomy, over the previously introduced guidewire,until the balloon of the dilatation catheter is properly positionedacross the lesion. Once properly positioned, the dilatation balloon isinflated with fluid one or more times to a predetermined size atrelatively high pressures (e.g. greater than 8 atmospheres) so that thestenosis is compressed against the arterial wall and the wall expandedto open up the passageway. Generally, the inflated diameter of theballoon is approximately the same diameter as the native diameter of thebody lumen being dilated so as to complete the dilatation but notoverexpand the artery wall. Substantial, uncontrolled expansion of theballoon against the vessel wall can cause trauma to the vessel wall.After the balloon is finally deflated, blood flow resumes through thedilated artery and the dilatation catheter can be removed therefrom.

In such angioplasty procedures, there may be restenosis of the artery,i.e. reformation of the arterial blockage, which necessitates eitheranother angioplasty procedure, or some other method of repairing orstrengthening the dilated area. To reduce the restenosis rate and tostrengthen the dilated area, physicians frequently implant a stentinside the artery at the site of the lesion. Stents may also be used torepair vessels having an intimal flap or dissection or to generallystrengthen a weakened section of a vessel. Stents are usually deliveredto a desired location within a coronary artery in a contracted conditionon a balloon of a catheter which is similar in many respects to aballoon angioplasty catheter, and expanded to a larger diameter byexpansion of the balloon. The balloon is deflated to remove the catheterand the stent left in place within the artery at the site of the dilatedlesion. Stent covers on an inner or an outer surface of the stent havebeen used in, for example, the treatment of pseudo-aneurysms andperforated arteries, and to prevent prolapse of plaque. Similarly,vascular grafts comprising cylindrical tubes made from tissue orsynthetic materials such as polyester, expanded polytetrafluoroethylene,and DACRON may be implanted in vessels to strengthen or repair thevessel, or used in an anastomosis procedure to connect vessels segmentstogether.

In the design of catheter balloons, characteristics such as strength,compliance, and profile of the balloon are carefully tailored dependingon the desired use of the balloon catheter, and the balloon material andmanufacturing procedure are chosen to provide the desired ballooncharacteristics. A variety of polymeric materials are conventionallyused in catheter balloons. Use of polymeric materials such as PET thatdo not stretch appreciably consequently necessitates that the balloon isformed by blow molding, and the deflated balloon material is foldedaround the catheter shaft in the form of wings, prior to inflation inthe patient's body lumen. However, it can be desirable to employballoons, referred to as formed-in-place balloons, that are not foldedprior to inflation, but which are instead expanded to the workingdiameter within the patient's body lumen from a generally cylindrical ortubular shape (i.e., essentially no wings) that conforms to the cathetershaft.

Catheter balloons formed of expanded polytetrafluoroethylene (ePTFE),which are inflated within the patient's body lumen without blow moldingthe ePTFE tubing, have been disclosed. Prior methods of forming theePTFE balloon involved wrapping a sheet of ePTFE on a mandrel and thenheating the wrapped sheet to fuse the layers of wrapped materialtogether. One difficulty has been the failure of the bond between theePTFE balloon and the catheter shaft at relatively low inflationpressures.

It would be a significant advance to provide a catheter balloon withimproved performance characteristics and ease of manufacture.

SUMMARY OF THE INVENTION

This invention is directed to an expandable medical device or componentthereof with a tubular body formed of a wrapped sheet of porouspolymeric material fused together, the tubular body having a fused seamat an angle relative to the longitudinal axis of the tubular body, andthe angle of the fused seam changes along the length of the tubular bodyfrom a first angle to a second angle greater than the first angle. Thesheet of porous polymeric material is wound and then fused together suchthat the winding angle in a first longitudinal section of the tubularbody is less than the winding angle in a second longitudinal section ofthe tubular body, in order to provide the second section with greaterresistance to expansion (i.e., lower compliance) than the first section.

In a presently preferred embodiment, the tubular body has a centrallylocated section with the fused seam at the first angle. In oneembodiment, the tubular body has a distal section with the fused seam atthe second angle greater than the first angle (i.e., the second angle ismore nearly perpendicular relative to the longitudinal axis of thetubular body than is the first angle). Typically, a proximal section ofthe tubular body has the fused seam at a third angle greater than thefirst angle. The second and third angles are preferably about equal,although in alternative embodiments the third angle can be less than orgreater than the second angle. In one embodiment, the angle of the fusedseam changes from the first angle to an intermediate angle between thefirst and second angles, to provide multiple changes in the resistanceto expansion along the length of the tubular body. Similarly, in oneembodiment, the angle of the fused seam changes from the first angle toan intermediate angle between the first and third angles.

In a presently preferred embodiment, the expandable medical device is aninflatable balloon for a catheter. The balloon can be used on a varietyof suitable balloon catheters including coronary and peripheraldilatation catheters, stent delivery catheters, drug delivery cathetersand the like. Although discussed below primarily in terms of theembodiment in which the medical device is an inflatable member such as aballoon for a catheter, it should be understood that other expandablemedical devices are included within the scope of the invention,including stent covers and vascular grafts. The catheter balloontypically has a proximal skirt section and a distal skirt section bondedto the catheter shaft so that the interior of the balloon is in fluidcommunication with an inflation lumen in the shaft. The balloon has aninflatable working section between the skirt sections which expandsduring inflation of the balloon to perform a procedure such as dilatinga stenosis or implanting a stent, and has inflated sections on eitherend of the inflated central working section tapering towards the skirtsections.

In a presently preferred embodiment, the fused seam at the first angleextends along at least a portion of the balloon working section, and thefused seam at the second angle extends along at least a portion of oneof the proximal or distal skirt sections. For example, in oneembodiment, at least a portion of the distal skirt section has the fusedseam at the second angle greater than the first angle, and at least aportion of the proximal skirt section has the fused seam at the thirdangle greater than the first angle. Thus, the skirt sections, with thefused seam of the porous polymeric material at the second angle greaterthan the first angle relative to the longitudinal axis of the balloon,have a greater resistance to expansion than the working length duringinflation of the balloon. As a result, the burst pressure of the balloonis increased because the bond strength of the skirt sections isincreased. The higher wrap angle of the skirt sections is believed toprovide increased resistance to radial expansion by inhibiting thetendency of the angle of fused seam to increase due to rotation of thewrapped porous polymeric sheet during inflation of the balloon. In oneembodiment, the balloon has a burst pressure (bond seal strength) ofabout 200 to about 350 psi, preferably about 250 to about 350 psi Inaddition to an improved, increased burst pressure, the increased bondstrength in a preferred embodiment provides increased fatigue resistanceso that the balloon can be inflated multiple times without the bondbetween the balloon and shaft failing.

The proximal and distal inflatable sections (commonly referred to as thetapered or cone sections of the inflated balloon), located between theskirt sections and the central working section, may have the fused seamat the first angle, the second and third angles, or an intermediateangle between the first angle and the second and third angles along allor a portion of the lengths thereof. For example, in one embodiment, afirst portion of the inflatable distal section has the fused seam withthe second angle, and a second portion of the inflatable distal sectionhas the fused seam with an intermediate angle between the first angleand the second angle. Consequently, the proximal and distal inflatablesections which are located at either end of the working length and whichinflate to a tapered configuration are provided with more resistance toexpansion than the working length, and expand to a smaller diameter thanthe working length, to further increase to burst pressure of theballoon.

In a presently preferred embodiment, the wrapped sheet of porouspolymeric material comprises a polymer selected from the groupconsisting of expanded polytetrafluoroethylene (ePTFE), an ultra highmolecular weight polyolefin such as ultra high molecular weightpolyethylene, porous polyethylene, porous polypropylene, porouspolyurethane, and porous nylon. In one embodiment, the porous materialhas a node and fibril microstructure. For example, ePTFE and ultra highmolecular weight polyethylene (also referred to as “expanded ultra highmolecular weight polyethylene”) typically have a node and fibrilmicrostructure, and are not melt extrudable. The node and fibrilmicrostructure, when present, is produced in the material usingconventional methods. In the embodiment in which the polymeric materialof the balloon has a node and fibril microstructure, after the fusedseam is formed, the tubular body of porous polymeric material istypically further processed, as for example by being stretched, heated,compacted, and heated a final time, to form the balloon. However, avariety of suitable polymeric materials can be used in the method of theinvention, including conventional catheter balloon materials which aremelt extrudable. In one presently preferred embodiment, the polymericmaterial cannot be formed into a balloon by conventional balloon blowmolding, and is formed into a balloon by bonding wrapped layers of thepolymeric material together to form a tubular member, and preferablyprovided with a nonporous second layer or liner, to form an inflatableballoon.

In a method of making an expandable medical device or component thereofwhich embodies features of the invention, a sheet of porous polymericmaterial is wrapped, typically on a mandrel, to form a tube having aseam formed by adjacent edges of the sheet, a longitudinal axis, a firstlongitudinal section with the seam at a first angle relative to thelongitudinal axis of the tubular body, and a second longitudinal sectionwith the seam at a second angle greater than the first angle relative tothe longitudinal axis of the tubular body. The tube is heated, as forexample in an oven, to fuse the longitudinal edges of the wrapped sheettogether, to form a tubular body having a fused seam.

The wrap angle is dependent upon the inner diameter of the resultingtubular body (i.e., the outer diameter of the mandrel on which the sheetis wrapped), and the width of the sheet of porous polymeric material,and the amount of overlap (if any) between the longitudinally adjacentwrapped portions of the sheet. In a presently preferred embodiment, thewidth of the sheet of porous polymeric material is substantially uniformalong the length of the sheet. The substantially uniform width of thesheet may vary within the tolerances used for forming the sheet, andthus the width may vary typically by about ±5% along the length of thesheet. In order to change the wrap angle at a transition between thesections having different wrap angles the sheet of porous polymericmaterial is typically stretched and/or the amount by which the edge ofthe wrapped sheet overlaps the edge of the longitudinally adjacentportion of wrapped material is changed as the sheet is wrapped aroundthe mandrel. However, a variety of methods may be used to increase thewrap angle, such as for example using a sheet having a varying width(i.e., a greater width in the portion of the length of the sheet formingthe second section of the tubular body), or by wrapping the sheet on avarying diameter mandrel. In one embodiment, the sheet is wrapped suchthat the adjacent edges abut one another at least along the firstsection (i.e., the section having the fused seam at the first angle).However, in alternative embodiments, the sheet is to wrapped such thatthe adjacent edges of the wrapped sheet along the first section are inan overlapping configuration, although typically with a lesser amount ofoverlap than in the remaining sections with the fused seam at a higherangle.

The sheet of polymeric material is wrapped along the length of themandrel, and is typically wrapped multiple times back over theunderlying length or layer in the opposite direction, to form multiplelayers of the porous material which typically fuse together duringformation of the fused seam. Thus, the tubular body typically comprisesmultiple layers of the wrapped sheet, with adjacent layers of thewrapped sheet having the fused seam at the given angle of thelongitudinal section but oriented in opposite directions. In oneembodiment, during formation of the porous polymeric tubular body, thesheet of porous polymeric material is wrapped so that the first angle ofthe wrapped seam along a first longitudinal section is about 60 to about75 degrees, preferably about 60 to about 70 degrees, and the secondangle along a second longitudinal section is greater than the firstangle and is about 70 to about 89 degrees, preferably about 75 to about85 degrees. The wrapped sheet is then heated to fuse the wrapped seamand form the porous polymeric tubular body. However, in the embodimentin which the device component is a balloon, the resulting porouspolymeric tubular body is typically stretched and/or compacted, orotherwise further processed, so that the angle of the fused seam may beincreased or decreased along at least a portion of the length of thetubular body. The wrap angle decreases, and typically by about 30 toabout 90 percent, more specifically about 70 to about 80 percent, as aresult the porous polymeric tube being longitudinally stretched afterformation of the fused seam. For example, in one embodiment, the wrapangle along the first section (i.e., the first angle) is originallyabout 60 to about 70 degrees after formation of the fused seam, andthereafter is caused to decrease to about 15 to about 25 degrees as aresult of the porous polymeric tube being longitudinally stretched. Inone embodiment, the porous polymeric tube is longitudinally compacted,typically after being longitudinally stretched, causing the wrap angleto increase as a result of the longitudinal compaction. Although theabsolute value of the wrap angle of the fused seam may change as aresult of such subsequent processing following the wrapping and fusingwhich forms the fused seam, the wrap angle of the fused seam in thefinished balloon will remain greater in the second section than in thefirst section. For example, in one embodiment, first angle of the fusedseam of the finished balloon (after any stretching or compactingprocessing) is about 10% to about 80% of the second angle and preferably10% to about 50% of the second angle. In one embodiment, the fused seamof the finished balloon has a first angle of about 15 to about 75degrees and preferably about 15 degrees to about 35 degrees, and asecond angle (greater than the first angle) of about 25 to about 89degrees and preferably about 50 degrees to about 89 degrees.

The expandable medical device or component thereof is provided withvariable resistance to expansion along the length thereof due to thevarying wrap angle of the porous polymeric sheet. In the embodiment inwhich the porous polymeric sheet forms a layer of a catheter balloonhaving at least one layer, the strength of the bond between the balloonand the catheter shaft is increased. Moreover, the working length of theballoon and tapered sections inflate to more clearly delineated sectionsdue to the varying wrap angle, with the well defined working lengthfacilitating stent positioning in the embodiment in which the ballooncatheter is used for stent delivery. These and other advantages of theinvention will become more apparent from the following detaileddescription and accompanying exemplary figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an elevational view, partially in section, of a stentdelivery balloon catheter embodying features of the invention.

FIG. 1B illustrates the balloon of FIG. 1A fully inflated.

FIGS. 2 and 3 are transverse cross sectional views of the ballooncatheter shown in FIG. 1, taken along lines 2-2, and 3-3, respectively.

FIG. 4 is an elevational view of an assembly of a sheet of porouspolymeric material wrapped on a mandrel to form a tube during formationof a layer of the balloon of FIG. 1, in which the sheet has a seam witha first angle at a central section of the tube and a second angle at endsections of the tube.

FIG. 5 illustrates the assembly shown in FIG. 4, partially inlongitudinal cross section.

FIG. 6 is a transverse cross sectional view of the assembly shown inFIG. 5, taken along line 6-6.

FIG. 7 is an elevational view of an assembly of a sheet of porouspolymeric material wrapped on a mandrel during formation of a layer ofthe balloon of FIG. 1 in an alternative embodiment in which the sheethas a seam with an intermediate angle between the first angle of thecentral section and the second angle of the end sections.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A illustrates an over-the-wire type stent delivery ballooncatheter 10 embodying features of the invention. Catheter 10 generallycomprises an elongated catheter shaft 12 having an outer tubular member14 and an inner tubular member 16. Inner tubular member 16 defines aguidewire lumen 18 configured to slidingly receive a guidewire 20, andthe coaxial relationship between outer tubular member 14 and innertubular member 16 defines annular inflation lumen 22, as best shown inFIG. 2 illustrating a transverse cross section view of the distal end ofthe catheter shown in FIG. 1A, taken along line 2-2. An inflatableballoon 24 disposed on a distal section of catheter shaft 12 has aproximal skirt section 25 sealingly secured to the distal end of outertubular member 14 and a distal skirt section 26 sealingly secured to thedistal end of inner tubular member 16, so that its interior is in fluidcommunication with inflation lumen 22. An adapter 30 at the proximal endof catheter shaft 12 is configured to provide access to guidewire lumen18, and to direct inflation fluid through arm 31 into inflation lumen22. In the embodiment illustrated in FIG. 1A, the balloon 24 is shownprior to being fully inflated in a patient's body lumen 27, and with anexpandable stent 32 having expandable tubular stent cover 35 mountedthereon. The distal end of the catheter may be advanced to a desiredregion of a patient's body lumen 27 in a conventional manner and balloon24 may be inflated to expand covered stent 32, seating the covered stent32 in the body lumen 27. FIG. 1B illustrates the balloon catheter 10 ofFIG. 1A, with the balloon 24 fully inflated to expand the covered stent32 within the body lumen 27. Inflated balloon 24 has a centrally locatedworking length with stent 32 thereon, and proximal and distal inflatablesections (i.e., inflated tapered sections) at either end of the workinglength between the working length and the respective skirt section 25,26 of the balloon

In the embodiment illustrated in FIG. 1, balloon 24 has a first layer 33and a second layer 34. In a presently preferred embodiment, the balloon24 has at least one layer comprising a porous polymeric material, andpreferably a microporous polymeric material having a node and fibrilmicrostructure, such as ePTFE. In the embodiment illustrated in FIG. 1,first layer 33 is formed of ePTFE, and the second layer 34 is formed ofa polymeric material preferably different from the polymeric material ofthe first layer 33. Although discussed below in terms of one embodimentin which the first layer 33 is formed of ePTFE, it should be understoodthat the first layer may comprise other materials including ultrahighmolecular weight polyethylene. The second layer 34 is preferably formedof an elastomeric material, including polyurethane elastomers, siliconerubbers, styrene-butadiene-styrene block copolymers, polyamide blockcopolymers, and the like. In a preferred embodiment, layer 34 forms aninner layer of balloon 24, although in other embodiments it may be onthe exterior of the layer 33. Layer 34 limits or prevents leakage ofinflation fluid through the microporous ePTFE layer 33 to allow forinflation of the balloon 24, and expands elastically to facilitatedeflation of the balloon 24 to a low profile deflated configuration. Thelayer 34 may consist of a separate layer which neither fills the poresnor disturbs the node and fibril structure of the ePTFE layer 33, or itmay at least partially fill the pores of the ePTFE layer 33.

The ePTFE layer 33 is formed according to a method which embodiesfeatures of the invention, in which a sheet of ePTFE is wrapped to forma tube, and then heated to fuse the wrapped material together. Inaccordance with a method of the invention, the sheet is wrapped suchthat the wrap angle varies along the length of the tube.

FIG. 4 illustrates an assembly of a sheet 40 of porous polymericmaterial (e.g., ePTFE) wrapped around a mandrel 41 and fused to form aporous polymeric tube, during the formation of the ePTFE layer 33 of theballoon 24 of FIG. 1. In the embodiment of FIG. 4, the tube has acentrally located section 44 with the fused seam 43 at a first angle ofabout 63 to about 65 degrees relative to the longitudinal axis of thetube, and a first end section 45 with the fused seam 43 at a secondangle of about 76 to about 78 degrees, and a second end section 46 withthe fused seam 43 a third angle about equal to the second angle.Although illustrated at about 76 degrees in FIG. 4, it should beunderstood that in a presently preferred embodiment the second angle ispreferably as close to 90 degrees as possible while allowing the sheet40 to progress helically along the length of the mandrel 41.Additionally, although the fused seam 43 is illustrated in FIG. 4 ashighly visible lines along the tube for ease of illustration, it shouldbe understood that the fused seam 43 in the finished balloon isgenerally not highly visible to the naked eye. FIG. 5 illustrates alongitudinal cross sectional view of the assembly of FIG. 4, and FIG. 6illustrates a transverse cross sectional view of the assembly of FIG. 5,taken along lines 6-6.

Preferably the centrally located section 44 of the tube of FIG. 4corresponds to the inflatable sections of the balloon 24 of FIG. 1(i.e., the inflatable working length with the stent 32 mounted thereon,and the inflated proximal and distal tapered sections on either end ofthe working length). The first and second end sections 45, 46 correspondto the proximal and distal skirt sections 25, 26 of balloon 24 of FIG.1, which are secured to the catheter shaft 12. The angles illustrated inFIG. 4 are the angles which are present following wrapping and fusing ofthe sheet prior to any further processing steps, such as longitudinallystretching and/or compacting the porous polymeric tube, which may changethe wrap angles. Additionally, inflation of the balloon typicallyincreases the first wrap angle of the central section of the balloon asthe wrapped sheet unwinds during expansion.

The sheet 40 of polymeric material is preferably wrapped along a lengthof the mandrel 41 to form at least one layer of wrapped material. In apresently preferred embodiment, multiple layers of polymeric materialare wrapped on the mandrel, by wrapping the sheet 40 down the length ofthe mandrel 41 to form a first layer and then back again over the firstlayer one or more times to form additional layers, which in oneembodiment results in three to five layers, preferably about four layersof material forming the ePTFE layer 33 of balloon 24. Thus, althoughillustrated in FIG. 5 as a single layer of wrapped material, it shouldbe understood that the sheet 40 typically forms multiple layers on themandrel 41. The multiple layers of ePTFE are typically fused together toproduce the tube forming layer 33 of balloon 24. Because the adjacentlayers of the sheet are wrapped in opposite directions along the lengthof the mandrel, the adjacent layers have the fused seam oriented inopposite directions. However, the respective angles of the fused seam(i.e, first, second or third angles) of the various longitudinalsections of the tube remain the same in the adjacent layers, although inopposite directions.

In the embodiment of FIG. 1, the sheet 40 is a long strip of polymericmaterial having longitudinal edges along the length of the strip whichare longer than the width of the sheet 40. The sheet 40 is wrapped onthe mandrel 41 so that the longitudinal edges of the sheet 40 arebrought together in an abutting or overlapping relation, and the fusedseam 43 joins the abutting or overlapping edges together. In a presentlypreferred embodiment, the fused seam 43 is formed by edges of thewrapped sheet 40 which abut oneanother, at least along the centrallylocated section 44.

In order to transition from the first angle to the second/third angleduring wrapping of the sheet 40 from one end to the other end of themandrel 41, the sheet 40 is typically stretched and/or caused to overlapa portion of the preceding turn of the sheet 40 in a transition section.In the embodiment illustrated in FIG. 5, portions of the preceding turnsof the sheets are covered by the adjacent turn of the sheet in thetransition sections and in the first and second end sections 45, 46, inorder to form the first and second angles. Although FIG. 5 illustratesan embodiment in which the edges of the sheet 40 overlap oneanotheralong the first and second end sections 45, 46, to form the seam havinga larger angle than the seam along the central section 44, it should beunderstood that in alternative embodiments the edges of the sheet abutoneanother along the first and second end sections 45, 46, as forexample by the sheet 40 being stretched (to change the width of thesheet) during winding of the first and second end sections 45, 46. Inthe embodiment of FIG. 5, the width of the sheet 40 and the outerdiameter of the mandrel 41 are such that the sheet 40 can be wrappedwith abutting edges forming the seam at an angle of about 65 degrees inthe central section 44.

In the embodiment of FIGS. 4 and 5, the fused seam angle transitionsdirectly from the first to the second angle. However, in alternativeembodiments, an intermediate longitudinal section is provided betweenthe section with the fused seam at the first angle and the othersections of the tube, the intermediate section having an intermediateangle greater than the first angle and less than the second/thirdangles. The intermediate angle provides a section having greaterresistance to expansion than the section with the fused seam at thefirst angle, and less resistance to expansion than the sections with thesecond/third angles. FIG. 7 illustrates an assembly of a wrapped sheet40 of porous polymeric material on mandrel 41, with proximal and distalintermediate sections 47, 48 having the fused seam at an intermediateangle between the first and second/third angles. In the embodiment ofFIG. 7, the intermediate angle is about 70 degrees, although a varietyof suitable intermediate angles may be used. In one embodiment, thesheet 40 of porous polymeric material is wrapped so that theintermediate angle, prior to any stretching or compacting of the porouspolymeric tube, is about 65 to about 85 degrees, more particularly about68 to about 75 degrees. The intermediate angle in the finished balloon(after any stretching and/or compacting of the porous polymeric tube) istypically about 85% to about 95% of the second angle, and morespecifically is typically about 20 to about 85 degrees. The intermediatesections 47, 48 correspond at least in part to the inflatable proximaland distal sections (i.e., inflated tapered sections) at either end ofthe working length of the balloon 24 in FIG. 1B. Although illustrated inFIG. 7 with the fused seam angle varying from about 78 degrees at theend sections 45, 46, to about 70 degrees at the intermediate sections47, 48, and further to about 63 degrees at the central section 44, itshould be understood that a tube with a variable fused seam angle inaccordance with the invention may have a variety of sections with avariety of angles. The transitions between the intermediate sections 47,48 and the adjacent longitudinal sections are formed as discussed abovein relation to the embodiment of FIG. 5.

The sheet 40 is preferably a polymeric material having a microporousstructure, which in one embodiment has a node and fibril structure, suchas ePTFE. The sheet 40 preferably has the desired microstructure (e.g.,porous and/or node and fibril) before being wrapped on the mandrel 41.In a presently preferred embodiment, the sheet 40 of ePTFE ispartially-sintered before wrapping.

After the fused seam 43 is formed, the tubular body is typically furtherprocessed prior to being bonded to the layer 34 to form the balloon 24.Preferably, the tubular body is further processed by being stretched,sintered, compacted, and then sintered again, to provide the desiredproperties such as the desired dimension, and dimensional stability(e.g., to minimize changes in length occurring during inflation of theballoon). For example, in one embodiment, the tubular body islongitudinally stretched to thereby increase the length of the tubularbody by about 50% to about 200%. After the longitudinal stretching, thetubular body is preferably compacted and heated to further sinter thematerial, to provide the desired performance characteristics for balloon24. The tubular body is typically heated in an oven at about 360° C. toabout 380° C., or to at least the melting point of the ePTFE. Thestretching and/or compaction typically affects the angle of the fusedseam. In one embodiment, the finished balloon layer 33 (prior toinflation of the balloon), produced from the tube of FIG. 7 having thefused seam at the angles shown in FIG. 7, has the fused seam at anglesalong at least some of the sections 44, 45, 46, 47, 48 which are lessthan the angles shown in FIG. 7 as a result of the further processing.The completed ePTFE layer 33 is then bonded to or otherwise combinedwith the elastomeric liner 34 to complete the balloon 24 with theballoon 24 secured to the catheter shaft 12.

The dimensions of catheter 10 are determined largely by the size of theballoon and guidewires to be employed, catheter type, and the size ofthe artery or other body lumen through which the catheter must pass orthe size of the stent being delivered. Typically, the outer tubularmember 14 has an outer diameter of about 0.025 to about 0.04 inches(0.064 to 0.10 cm), usually about 0.037 inches (0.094 cm), the wallthickness of the outer tubular member 14 can vary from about 0.002 toabout 0.008 inches (0.0051 to 0.02 cm), typically about 0.003 to 0.005inches (0.0076 to 0.013 cm). The inner tubular member 16 typically hasan inner diameter of about 0.01 to about 0.018 inches (0.025 to 0.046cm), usually about 0.016 inches (0.04 cm), and wall thickness of 0.004to 0.008 inches (0.01 to 0.02 cm). The overall length of the catheter 10may range from about 100 to about 150 cm, and is typically about 143 cm.Balloon 24 typically has a length of about 5 to about 60 mm, and aninflated working diameter of about 2 to about 10 mm. In one embodiment,the skirt sections 25, 26 of the balloon 24 typically have a length ofabout 0.5 to about 7 mm, and the central working section of the balloon24 has a length greater than the skirt sections and equal to about 5 toabout 40 mm.

Inner tubular member 16 and outer tubular member 14 can be formed byconventional techniques, for example by extruding and necking materialsalready found useful in intravascular catheters such a polyethylene,polyvinyl chloride, polyesters, polyamides, polyimides, polyurethanes,and composite materials. The various components may be joined usingconventional bonding methods such as by fusion bonding or use ofadhesives. Although the shaft is illustrated as having an inner andouter tubular member, a variety of suitable shaft configurations may beused including a dual lumen shaft having a side-by-side lumens therein.Similarly, although the embodiment illustrated in FIG. 1 is anover-the-wire stent delivery catheter, balloons of this invention mayalso be used with other types of intravascular catheters, such as rapidexchange dilatation catheters. Rapid exchange catheters generallycomprise a distal guidewire port in a distal end of the catheter, aproximal guidewire port in a distal shaft section distal of the proximalend of the shaft and typically spaced a substantial distance from theproximal end of the catheter, and a short guidewire lumen extendingbetween the proximal and distal guidewire ports in the distal section ofthe catheter.

While the present invention is described herein in terms of certainpreferred embodiments, those skilled in the art will recognize thatvarious modifications and improvements may be made to the inventionwithout departing from the scope thereof. Moreover, although individualfeatures of one embodiment of the invention may be discussed herein orshown in the drawings of the one embodiment and not in otherembodiments, it should be apparent that individual features of oneembodiment may be combined with one or more features of anotherembodiment or features from a plurality of embodiments.

1-23. (canceled)
 24. A method of making an expandable medical device orcomponent thereof having a tubular body, comprising: a) wrapping a sheetof porous polymeric material to form a tube having a seam of adjacentedges, a longitudinal axis, a first longitudinal section with the seamat a first angle relative to the longitudinal axis of the tubular body,and a second longitudinal section with the seam at a second anglegreater than the first angle relative to the longitudinal axis of thetubular body; and b) heating the tube, to fuse the edges together toform a tubular body having a fused seam.
 25. The method of claim 24wherein the width of the sheet of porous polymeric material varies alongthe length of the sheet, and wrapping the sheet comprises spirallywrapping the sheet on a substantially uniform diameter mandrel.
 26. Themethod of claim 24 wherein the width of the sheet of porous polymericmaterial is substantially uniform along the length of the sheet, andwrapping the sheet comprises spirally wrapping the sheet on a uniformdiameter mandrel so that the edges of the sheet have a smaller amount ofoverlap in the first section than at a transition between the firstsection and the second section.
 27. The method of claim 24 wherein theseam is formed by edges of the sheet which abut oneanother, and wrappingthe sheet includes overlapping portions of the sheet in at least atransition between the first section and the second section.
 28. Themethod of claim 24 wherein the medical device component is a catheterballoon and including, after forming the fused seam, longitudinallystretching the tubular body and thereby increasing the angle of the seamof the first and second sections.
 29. The method of claim 24 wherein a)comprises wrapping the sheet so that the first angle is about 60 toabout 75 degrees.
 30. The method of claim 29 wherein a) compriseswrapping the sheet so that the second angle is about 70 to about 89degrees.